Search for WHSP γ-ray counterparts within Fermi-LAT data: Solving a case of source confusion

Abstract

In an attempt to unveil faint γ-ray blazars our group uses the position of high synchrotron peak blazars (HSP) as seeds for running likelihood analysis with the Fermi Science Tools. Mainly, our candidates are part of the 1/2WHSP catalogs, which were built by multi-frequency selections schemes and are currently the largest samples of HSP blazars. Usually the new γ-ray sources are faint, and just above the threshold for detectability with Fermi-LAT, therefore hard to identified by automated search methods. Studying the TS maps to validate new γ-ray detections we end up discovering a few cases where the WHSP γ-ray signature is confused with sources from the 3FGL catalog. We were able to disentangle their signals by building TS maps in different energy bands, taking advantage of cases where sources have distinct spectral slope (Γ 0.3−500GeV ) therefore dominate in distinct energy bands. Here we show an example for the 1WHSP J041458.1-533943 which is confused with 3FGL J0413.6-5334.